Superconducting flux flow transistors (SFFT) are active four terminal devices exhibiting very high speed operation and a large gain which makes such transistors suitable for many applications. Conventional superconducting flux flow transistors are disclosed by J. S. Martens et al. in "S-Parameter Measurements and Application of Superconducting Flux Flow Transistors", 1991, IEEE MTT-S Digest, pp. 1231-34, and by G. K. G. Hohenwarter et al. in "Characteristics of Superconducting Flux-Flow Transistors", March 1991, IEEE Transactions on Magnetics, Vol. 27, No. 2, pp. 3297-3300. The entire disclosures of both of these references are incorporated herein by reference.
Superconducting flux flow transistors may be used as the active element in various devices including amplifiers, oscillators and mixers. A magnetic field generated by current in a control line controls operation of the transistor similar to a field effect transistor which is controlled by an electric field. The output or terminal voltage varies with respect to the magnitude of current in the transistor's control line. In a conventional superconducting flux flow transistor, the configuration of the control line is an inefficient manner of increasing the output or terminal voltage.